(a) Field
The present disclosure relates to a display device and a method for driving the same, and more particularly, to a liquid crystal display device and a method for driving the same.
(b) Description of the Related Art
A liquid crystal display is one of the most widely used flat panel displays at present. Generally, a liquid crystal display includes two display panels including field generating electrodes such as a pixel electrode and a common electrode, and a liquid crystal layer interposed therebetween. The liquid crystal display generates an electric field in the liquid crystal layer by applying a voltage to the field generating electrodes. The alignment of liquid crystal molecules of the liquid crystal layer changes through the generated electric field and the liquid crystal display displays images by controlling polarization of incident light. The liquid crystal display also includes a switching element that is connected to each pixel electrode, and a plurality of signal lines such as a gate line and a data line for applying a voltage to the pixel electrode by controlling the switching element.
Among various types of liquid crystal displays, a vertically aligned mode liquid crystal display uses long axes of liquid crystal molecules. The liquid crystal modules are aligned to be vertical to upper and lower display panels when no electric field is applied, but their alignment changes when an electric field is applied. The vertically aligned mode liquid crystal display has a large contrast and a wide reference viewing angle. For example, the reference viewing angle indicates a viewing angle in which the contrast ratio is 1:10 or a luminance inversion limit angle between grays.
The wide reference viewing angle in the vertically aligned mode liquid crystal display may be achieved by forming a cut portion in the electric field generating electrode and forming protrusions above or below the electric field generating electrode. Since the cut portion and the protrusions determine a tilt direction of the liquid crystal molecules, the cut portion and the protrusions are appropriately placed to scatter the tilt direction of the liquid crystal molecules in various directions, thereby widening the reference viewing angle.
Further, a front visibility of the vertically aligned mode liquid crystal display is typically lower than a side visibility. For example, in the case of a patterned vertically aligned mode liquid crystal display with a cut portion, an image becomes brighter toward the side, and as a result, when the image is too bright, there is no difference in luminance between high grays. As a result, a picture may look distorted.
In an effort to approximate a side visibility to a front visibility of a vertically aligned mode liquid crystal display, a method for varying transmittance by dividing one pixel into two subpixels and applying different voltages of the two subpixels was proposed. However, when one pixel is divided into two subpixels, and the side visibility is approximated to the front visibility by varying transmittance, luminance is increased at a low gray or a high gray, and a gray expression at the side becomes difficult. As a result, an image quality may deteriorate. Further, when the transmittance variation is not definite with variation in gray, the gray variation cannot be displayed. As a result, the image quality may also deteriorate. In general, when one pixel is divided into two subpixels, the transmittance is decreased by an interval between the two subpixels.
The above information disclosed in the background section is only for facilitating understanding of the background information of the present disclosure, therefore it may contain information that does not form a prior art that is already known to a person of ordinary skill in the art.